Today in buildings or any other constructions, the fire detecting system in which a number of fire detectors are distributed in a plurality of sections, a plurality of detectors in one section are connected to one alarming line for each section, and a plurality of alarming lines are connected to a receiving unit.
Conventionally, in order to test fire detectors in such a system, the inspector goes over to each place where a fire detector is installed, and confirm the operability of each fire detector by raising its temperature using, for instance, a cigarette lighter, or by generating smoke artificially. The test method in which an electrical change to actuate a fire detector is applied to the fire detector to be tested is also known. Even by this method, the inspector must go over to the place where the detector in question is installed. The electrical change can be supplied from the receiving unit side. But a plurality of fire detectors are connected to one alarming line, and therefore, the inspector cannot identify which detector has been actuated from the receiving unit side, and he cannot select and test a particular detector, either.
In the copending Patent Application Ser. No. 351,916, a selectively testable fire detector, which generates a signal voltage when said detector has counted the designated number of pulses sent forth from the receiving unit by way of the alarming line, is proposed. However, the fire detector of said application can only be designated by incremental numbers from the first one in an order but an arbitrarily selected one cannot be tested.
The purpose of this invention is to provide a selective test circuit for fire detectors in which the disadvantage in the prior art fire detector test circuits as mentioned above is eliminated and every fire detector can be selectively tested from the side of the receiving unit.